Almost all of Haiti's public buildings and utilities have been destroyed, including the Presidential Palace and the National Cathedral.

Normal communications were cut off, roads were blocked by rubble and trees, electric power was interrupted and water was in short supply. The only lights visible in the city came from solar-powered traffic signals.

Among the public buildings that collapsed were the main parliament building, tax headquarters and prison along with schools and hospitals. Haiti's president, Rene Preval, said he had nowhere to go after both the presidential palace and his own home were destroyed.

The headquarters of the UN, whose 9,000 peacekeepers have been stationed in Haiti since 2004 when President Jean-Bertrand Aristide was ousted, was also demolished.

As many as 100 UN staff -- including the mission head and his deputy -- remain missing and 36 have so far been confirmed dead. For the global organisation, it represented the greatest loss of life in a single event in its history.

Rubble

The archbishop of Port-au-Prince, Monsignor Joseph Serge Miot, was found dead in the wreckage of the archdiocese office. Archbishop Bernadito Auza, the apostolic envoy to Haiti, said: "The cathedral, the archbishop's office, all the big churches, the seminaries have been reduced to rubble."

Elisabeth Byrs, spokeswoman at the United Nations Office for the Co-ordination of Humanitarian Affairs, said that relief agencies faced a "major logistic challenge" on the ground.

Paul Garwood, of the World Health Organisation, said at least eight hospitals and health facilities in and around the city had been damaged or destroyed.

"Roads are blocked by rubble, so cars, vehicles, ambulances can't reach those in need," he said. "WHO staff, for example, are going by foot to the central drugs store to get essential medicines and take them to health facilities."

Haiti has no real construction standards and Port-au-Prince's mayor estimated a year ago that 60pc of the capital's structures were unsound..